1. Field of the Invention
The present invention relates to transporting large towers. More specifically, the present invention relates to a system and method for transporting large monopole towers and tower sections, such as towers used to support commercial wind turbines, using one or more railcars.
2. Description of the Related Art
Large-scale wind turbines are used to generate electrical power. Such wind turbines consist of a tall tower with a generator nacelle rotatably coupled about the top of tower's vertical axis. A rotor hub extends out a horizontal axis of the nacelle. Two or more turbine blades are connected to the rotor hub at right angles to the horizontal axis. During operation, prevailing winds cause the turbine blades to rotate about the rotor hub's horizontal axis. The rotational forces are coupled to a generator within the nacelle, which produces electricity. The nacelle rotates about the vertical axis of the tower to maintain the wind turbine blades in proper orientation to the direction of the prevailing winds.
The various components of a large-scale wind turbine may be manufactured at different geographic locations, which may be anywhere in the world. For example, a manufacturer who wishes to assemble a wind turbine generator tower in the United States may have the towers manufactured in Korea, the nacelles manufactured in Denmark and the blades manufactured in Germany. These components must then be transported to the ultimate power generation site, assembled, erected, and placed into operation. Since the manufacturing operations may be spread across the world, transportation of the components to the generation site may utilize all modes of transportation, including ships, barges, trains and trucks. The various components are expensive to manufacture, and include delicate components that must be protected and handled properly during transportation. The transportation issues are exacerbated in that the components may be transported using plural modes during their journey. For example, a wind turbine tower manufactured in Korea may travel by ship across the ocean, then via railroad to a location in the geographic area of the generation site, and then finally by truck to the ultimate destination. Mounting fixtures are needed to adapt the particular component being transported to each mode of transportation.
The evolution of technology and the economies of scale have lead to the development and deployment of large-scale wind turbines with larger and larger proportions. The power generation capacity of a large-scale wind turbine is directly related to the length of the turbine blades, which define the swept area and power capacity of the turbine. The turbine blade proportions, in turn, are determinative of the tower height, as are the prevailing wind conditions. Tower height and wind loading establish the tower's strength requirement. Generally, wind turbine towers will taper from the base to the top, as this provides the requisite strength with the minimum of material and fabrication cost. Transportation and fabrication constraints commonly dictate that tall towers be separated into plural tower sections, which are finally assembled at the generation site. Transportation of long towers and tower section presents significant challenges to transportation engineers, particularly in the case of railroads, where the railroad profile is tightly limited and the trains must traverse curved sections and complex rail yards. Additionally, the requirement to fix towers and tower sections to railcars during transport, particularly given the tapered profile, creates the need for specialized fixtures, and the corresponding expense in their fabrication and utilization. Thus it can be appreciated that there is a need in the art for a system and method addressing the problems related to transportation of long and heavy towers and tower sections via rail.